Qualia

1. Anti-physicalist arguments

The terms ‘quale’ and ‘qualia’ (plural) are most commonly used to characterize what may be called the qualitative, phenomenal or ‘felt’ properties of our mental states, such as the throbbing pain of my current headache, or the peculiar blue of the afterimage I am experiencing now. Qualitative properties can be more or less specific: the state I am in at the moment can be an example of a migraine, a headache, a pain, or, even more generally, a bodily sensation. Briefly, a mental state is considered to have qualitative properties just in case there is something it is like to be in it.

It seems undeniable that our sensations and perceptions have qualitative properties. However, many philosophers have claimed that the distinctive feels of pains, after-images and other sensations are so radically different from objective properties such as mass or length that they could not be identical with any physical or functional properties of the brain and nervous system. (Indeed, some theorists reserve the term qualia to denote those mental properties, if any, that are irreducibly qualitative: this is why disputes about the metaphysical nature of qualitative properties are sometimes characterized as disputes about whether there are qualia, rather than about what kind of properties qualia, in the metaphysically neutral sense introduced above, could be.) The view that qualitative properties are metaphysically unique has been supported by powerful argument, and may seem to be reinforced by common sense and introspection. If this view is true, however, the existence of qualia will be incompatible with a fully naturalistic account of the mind.

Anti-physicalists have argued against the identity of qualitative with physical (or functional) properties throughout the history of the philosophy of mind, but three arguments have been especially influential since the mid-1970s. The first, modelled upon Descartes’ well-known argument for the ‘real distinction’ between mind and body in the Sixth Meditation, (see Descartes, R. §8; Dualism) proposes that one could, under ideal epistemic circumstances, imagine or conceive of the qualitative features of one’s pains or perceptions in the absence of any specific physical or functional properties (and vice versa), and that properties that can be so conceived or imagined must be distinct. The second argument proposes that there are qualitative properties of mental states that one could not know about before actually experiencing states of that (or similar) kind, no matter how much knowledge one had about the physical and functional properties of brains and nervous systems: for example, despite having comprehensive knowledge of the relevant sciences, a person raised in an entirely black and white environment would not know what it is like to see red, and despite years of studying bat neuropsychology, we could not know what it is like to be a bat. Moreover, the argument continues, properties that do not afford this sort of knowledge could not be part of the subject matter of any of the objective sciences. The third argument states that no physical or functional characterization of sensations or perceptions could adequately explain why they feel the way they do, and that such an explanatory gap raises doubts about the identification of the properties in question. The conclusion of the first two arguments, of course, is that qualia could not be identical with physical or functional properties, and the conclusion of the third argument is that, at the very least, we have no reason to believe that these identities hold.

Although there are interesting differences between them, these arguments are linked (and can profitably be treated together) in that the first premise of each appears to depend upon the thesis (1) that there is no conceptual connection between qualitative terms or concepts and physicalistic terms or concepts. If there were such a connection, then it would be impossible, if one was fully educated and attentive, to conceive (for example) of a pain existing apart from the relevant physical or functional property, and it would be possible, at least in principle, to know all there is to know about pain without ever having experienced pain oneself; it would also be easy to explain why it feels a certain way to have the associated physical or functional property. The second premise also appears to depend upon a common thesis, namely, (2) that given this lack of connection, our use of qualitative terms or concepts commits us to (or, at the very least, suggests) the existence of irreducibly qualitative properties.